1. Field of the Invention
The present invention generally relates to an apparatus and method for monitoring the continued rotation of a non-magnetically attractive indicator, e.g., a rotating, plastic dial, disc, wheel or arm of a meter. The present invention is particularly useful for detecting the satisfactory operation of flow meters, e.g., meters used to determine the flow of fluids from oil and gas wells, in transmission lines and in chemical processing plants. More particularly, the present invention relates to an apparatus and method employing the rotation of a magnetically attractive material for actuating magnetic and electrical switches for producing signals indicative of satisfactory operation of the flow meter.
2. Description of the Background
The desirability of observing and controlling the flow of a fluid through a conduit from a great distance has long been recognized by those associated with the oil and gas, the fluid transmission and the chemical processing industries. These observations would permit operators and controllers to more closely monitor flow and to more quickly react to deviations and malfunctions.
For example, it is important to have an accurate record of the fluid being pumped from remote oil and gas wells. Typical recording systems include conventional flow detection and volume devices interconnected with conventional rotating dial meters. These meters comprise a plurality of geared dials for displaying a number indicative of the volume of fluid passing through the conduit. In order to avoid the loss of production or lost/inaccurate measurement of production, it is desirable to have a means for a centrally located controller to observe the operation of these meters. Such observation permits immediate shut down of any well showing abnormal production and immediate dispatch of a repair crew. This immediate reaction is quite valuable to the oil and gas producer.
Conventional monitoring systems have included an electrical switch actuated by the meter movement to produce a signal at the central location. This signal has been used to actuate a variety of functions, including actuating a central counter, actuating a sampling device in the conduit near the meter and resetting an alarm device. The alarm is often a simple timer which must be reset within a predetermined time indicative of satisfactory operation of the meter showing the expected fluid flow. Failure of the signal to reset the alarm within the predetermined flow indicates an abnormal condition and will trigger shut down of the well pump and visual and/or audio alarms. Exemplary conventional systems have employed a cam on the meter shaft to operate a plunger or to operate a spring loaded lever to produce the necessary electrical output. These systems produce drag on the meter mechanism and contain rubbing parts which wear out. More recently, systems have been developed which incorporate a reed switch actuated by a magnet disposed on the rotating dial of the meter. These systems are plagued by the extreme fragility of the reed switch, particularly in view of the harsh environment and rough handling to which these devices are typically subjected. Further, the magnet rotating in a predominantly steel environment also produces drag on the meter.
Accordingly, there has been a long felt but unfulfilled need within the industry for a rigid, dependable and accurate apparatus and method useful for monitoring the continued rotation of a meter dial.